OSHA Addresses the Dangers of Trenching and Excavation in Construction

Trenching and Excavation SafetyTrenching and excavation are widely recognized as among the most hazardous construction operations, resulting in an average of two deaths per month and hundreds of injuries each year due to trench collapses. OSHA has addressed construction-related trenching and excavation hazards by developing specific safety standards for the construction industry, making the requirements easier to understand and providing construction employers with various options for classifying soil and selecting employee protection methods.

Cave-ins pose the greatest risk in trenching and excavation operations, and are much more likely than other excavation-related accidents to result in worker fatalities. Other potential hazards include falls, falling loads, hazardous atmospheres, and incidents involving mobile equipment. One cubic yard of soil can weigh as much as a car.

There a many factors in determining the proper protective systems to reduce or eliminate trenching and excavation hazards, including soil classification, depth of cut, water content of soil, changes due to weather or climate, surcharge loads (e.g., other materials to be used in the trench) and other operations in the vicinity. Trenching protective systems include:

  • Benching – cutting the sides of an excavation to form one or a series of horizontal levels, or steps, usually with vertical or near vertical surfaces between levels;
  • Sloping – cutting back the trench wall at an angle inclined away from the excavation;
  • Shoring – installing aluminum hydraulic or other types of supports to prevent soil movement;
  • Shielding – using trench boxes or similar types of supports to prevent soil cave-ins.

For additional information on trenching and excavation safety, visit OSHA’s Trenching and Excavation webpage.

The OSHA Training Center is offering OSHA 3015 – Excavation, Trenching, and Soil Mechanics in Sacramento, CA, on July 14-16, and in Bakersfield, CA, on Sept. 21-23, 2015. Students will learn about practical soil mechanics and the relationship to the stability of shored and unshored slopes and walls of excavations. Various types of shoring, including hydraulic and wood timbers, are covered. Testing methods are demonstrated and a field exercise is conducted, allowing students to use instruments such as penetrometers, torvane shears and engineering rods.

About the OSHA Training Center

The OSHA Training Center at Chabot-Las Positas Community College District offers high quality Occupational Safety & Health Administration standards-based training for construction, maritime and general industry at its Center in Dublin, California, as well as locations throughout California, Arizona, Nevada, Hawaii and Guam. Programs offered include OSHA safety standards, Outreach Trainer courses, Cal/OSHA standards curriculum, environmental courses and customized on-site safety training. For more information, including a complete course schedule, visit the OSHA Training Center website or call (866) 936-OSHA (6742).


  1. I didn’t know that excavation could be so dangerous. How deep can you dig before you need to add protective systems? We have some work that needs to be done in our backyard, so I will make sure to hire a professional who knows what to do and how to stay safe. Thank you for this information.

    • Hi April,

      Trenching is EXTREMELY dangerous and cave-ins still result in numerous fatalities every year.Below is what both OSHA and CalOSHA has to say about when to use protective systems. In addition, you should always call 811 BEFORE you dig to ensure that you don’t hit any vital utility lines. Check here for more information http://usanorth811.org/

      If an excavation is more than 5 feet in depth, there must be a protective system in place while workers are present in the excavation. Excavations more than 4 feet in depth must
      have a way to get in and out, usually a ladder, for every 25 feet of horizontal travel.

      If the trench is five feet deep or more it must be shored or sloped. If there is a possibility of soil movement, even shallower trenches have to be shored. If you have doubt about it, shore/slope the trench.

      Hope this helps!

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